In recent years, the demand for communications capacity has increased dramatically. Governments, businesses and individuals produce prodigious quantities of information at ever increasing rates, and also stoke the demand for high speed transfers of data, voice and video signals. More powerful personal computers and software are now able to create large database, real-time video, graphics and multimedia files. While our ability to generate information has skyrocketed, our ability to distribute and exchange this information is limited by the embedded narrow band infrastructure of the existing local telephone systems. Although the world is wired with over a billion miles of copper and has tens of millions of miles of installed optical fiber, this network is severely constrained by the bottleneck which resides at the interface between the local telephone company and its customers' premises, i.e., the "last mile". The gradual addition of more optical fibers and the implementation of various compression technologies can ameliorate this critical fault in the existing communications environment, but ultimately at great cost and on a schedule which will require several decades for completion.
Several attempts to solve the problem of distributing information to large numbers of subscribers have met with mixed results.
U.S. Pat. No. 2,288,802 issued to John Hays Hammond in 1942 and entitled Signalizing System discloses a radio transmission system which employs a carrier wave that is transmitted in two substantially independent channels. The channels are "made independent" by using polarizations which propagate at right angles to each other. The carrier waves may also be modulated "by the same signal frequency, but with a predetermined phase relationship between the two modulations." See Hammond, Column 1, Lines 1-24.
U.S. Pat. No. 4,747,160, issued to Bernard Bossard on May 24, 1988 and entitled Low Power Multi-Function Cellular Television System describes a network of low power, substantially omni-directional cell node transmitters which communicate with a directional receiving antennas. Bossard's omni-directional transmitter imposes severe constraints on the ability of this system to provide diverse information services to many different customers.
One particular disadvantage of Bossard's system, which is due to its omni-directional signal, is the limitation of the system to compensate for rainfall in small portions of customer cells. Since the entire signal must be amplified at an omni-directional broadcast node, the system runs the risk of overpowering the signal to customers which are unaffected by the storm fronts. Bossard compensates for this constraint by limiting cell size.
Another severe limitation of the Bossard invention is the inability of the Bossard system to transmit to a single customer, or to transmit different signals to many different customers. The cell size in Bossard's system is also limited to the amount of power generated, which is dependent on the available (TWT) of about 100 watts. The base case for Bossard's system might be a quadratic cell for a "substantially" omni-directional system, in which a 100 watt TWT might be located in each of four quadrants of a broadcast cell, limiting the cell broadcast power to approximately 400 watts.
In 1977, Xerox Corporation initiated work on the Xerox Telecommunications Network (XTEN), a nationwide, high-speed, end-to-end, digital communications service. ATEN was designed to provide local data services using a combination of substantially omni-directional transmission from cell nodes and point-to-point return links from transceivers located at business premises. Local networks were to be connected by intercity satellite or terrestrial "backbone" facilities. See Xerox Petition for Rulemaking, filed with the Federal Communications Commission on Nov. 16, 1978. See also Xerox Comments on the DTS Notice of Proposed Rulemaking, filed with the Federal Communications Commission on Jan. 14, 1980.
Siemens Corporation received Patent No. 1,586,260 from the Federal Republic of Germany in 1977. This patent, entitled A Radio Telecommuncations System, discusses a system which connects stationary subscriber stations to a telecommunications network such as a public telephone network. A radio concentrator, assigned to a dial-operated exchange, is connected to the stationary subscribers via an omni-directional antenna. See Siemens '260, Column 1, Lines 9-13 and Lines 21-24.
Siemens was also awarded French Patent No. 1,024,523 entitled Reseau d'emetteurs dondes Ultra-courtes, which also pertains to transmission of radio and television programs. See Siemens '523, Resume, Colunin 4.
In June of 1982, George Jacobs published a paper entitled Low Power Television in IEEE Spectrum. Jacobs explains the impact of the development of short-range, low-cost television systems. FIG. 3 of his article reveals the components of a low-power television station designed to produce electromagnetic power of a kilowatt or less.
Donald Silverman offers an analysis of an integrated, end-to-end digital communications service which may be used to augment existing inter-city network facilities in his paper entitled The Digital Termination System Solution for High Speed Local Distribution. This paper was published in the January, 1983 edition of Microwave Journal.
The IEEE Spectrum published a paper in June, 1983 by George Cooper and Ray Nettleton entitled Cellular Mobile Technology: The Great Multiplier. This article discusses the advantages of a cellular mobile communications system, interference problems, narrowband modulation, digital transmission, space diversity techniques which reduce fading and spread-spectrum and frequency hopping methods.
In their paper entitled Multiple Access Digital Microwave Radio System for Local Subscribers, Nasatoshi Murakami et al. describe a radio communication system which provides point-to-multipoint digital transmission in a metropolitan area. See IEEE International Conference on Communications '83, June 1983, pp. b2.5.1.
In an article entitled Digital Termination Systems, Walter Urich and Ronald Bohm describe a common carrier service designed to provide flexible, low-cost digital communications within a community using a portion of the microwave spectrum. See Computerworld, Jun. 6, 1984, pages 35-38.
In U.S. Pat. No. 4,525,861 issued in 1985, Thomas Freeburg explains the details of his Zoned Data Communications System for Communicating Message Signals between Portable Radios and a Host Computer. This system serves a geographic area that is divided into a number of non-overlapping zones. Signals carrying alphanumeric information are conveyed among a general communications controller and a number of portable radios. See Freeburg, Abstract, Lines 1-9.
Douglas Morais describes a Radio Communication System Using Frequency Division Multiplexing for Transmission between a Master Station and a Plurality of Remote Stations in his U.S. Pat. No. 4,528,656, printed in 1985. Morais' point-to-multipoint radio communication system includes a master station and a number of remote stations which communicate using frequency division multiplexing.
Alfred Mack discusses his Radio Communication System in his U.S. Pat. No. 4,633,463, granted in 1986. Mack's invention pertains to tactical military applications, and includes at least one remote station associated with each of several central stations. Each central station is connected to an omni-directional antenna, while each remote station is connected to a directional antenna. Each central station transmits at a distinct frequency, and each remote station is tuned to receive only the one frequency which is transmitted by its associated central station. See Mack, Abstract, Lines 1-11.
Minoru Kawano was granted U.S. Pat. No. 4,704,733 for his Cell Enhancer for Cellular Radio Telephone System Having Diversity, Function in 1987. His invention concerns a cell enhancer for use by one cellular provider in a cellular radio-telephone system. This cell enhancer has an "up-stream" antenna system directed at the cell site for receiving the transmitted down-link signal from the cell site. See Kawano, Abstract, Lines 1-10 and Column 2, Lines 38-42.
John R. Mihelich published a paper entitled Mitchell Commits to Cellular Television Study in the February, 1991 edition of Private Cable. Mihelich discusses the prospects for universal multi-channel cellular television service.
Siemens holds German Patent No. 2659638, which is entitled Funksystem zum Anschlu.beta. ortsfester Teilnehmerstationen an ein Nachrichtennetz.
European Patent Application No. 86303185.2, by Acampora et al., describes a terrestrial radio system which utilizes spot beam time division multiple access and frequency re-use to provide communication services from a base station to remote customer within a system service region.
PCT Patent Application No. PCT/SE90/00681, by Ahl et al., describes a method and a communications system for local dynamically connectable digital synchronous multiplex service networks. PCT Patent Application No. PCT/DE93/00382, by Ritter et al., describes a mobile radio network with central cell beaming.
U.S. Pat. No. 4,785,450, by Bolgiano et al., describes a communication system that comprises a plurality of subscriber stations in RF communication with a base station having multiple sequentially repetitive time slots.
In the article entitled New AUTOPLEX Cell Site Paves The Way For Digital Cellular Communications, Hardy and Lemp describe a cell site that has distributed rather than centralized control.
European Patent Application No. 85307456.5, by Horne, describes a cryptographic system for a direct broadcast satellite network. Ascom Zelcom AG has filed European Patent Application No. 89117388.2, which is entitled Digitales Funkubertragungssystem fur ein aus Zellen aufgebautes Netz unter Verwendung der Bandspreiztechnik.
UK Patent Application No. GB 2 261 575 A, by Marsh et al., describes a method of establishing a telecommunications network between subscriber stations and their associated local station. The network is managed using a system controller.
The greatest barrier to selectively delivering information to millions of diverse consumers resides at the network-customer interface or "last mile" in the communications network. Overcoming the enormous expense and complexity of supplying specific types of information to many different kinds of customers over this "last mile" has presented a major challenge to the telecommunications industry. The development of an intelligent and versatile local, multiple-point distribution system would constitute a major technological advance and would satisfy a long felt need in the telephone, entertainment and information businesses.